The present invention relates to an orthodontic procedure to properly place brackets on human teeth. More specifically, it relates to a device for placement of the bracket with respect to the marginal ridges of the teeth.
The present invention relates to my previous invention described in U.S. Pat. No. 6,296,482 entitled xe2x80x9cOrthodontic Height Positioning Gauge with Rotatable Headsxe2x80x9d issued on Oct. 2, 2001. That patent describes a method for placement of orthodontic brackets on human teeth by locating them using a hand-held measurement device. That document is hereby incorporated by reference as though fully set forth. This previous invention describes a height gauge by which brackets are located on individual teeth by measuring the distance from the cusp tip of each tooth.
However, there is a problem with gauges of this type. Although the cusp tip is used as the point of reference for measurement, it is the marginal ridges of the teeth which are the true desired points of alignment for the brackets. This can create inaccuracies because ridge-to-cusp distances vary. Past height gauges may have the facility for compensating for different ridge-to-cusp tip distances, however this requires an additional degree of judgment on the part of the clinician which can introduce the possibility of yet greater error. Furthermore, these height gauges rest on the cusp tip and thus have only one point of contact. Therefore, they can easily be incorrectly angled so that the measurement taken is not accurate.
Given the state of the art in tooth measurement for proper orthodontic bracket placement, there is therefore a need for a device which directly determines the correct bracket placement on the facial surface of a human tooth using the tooth""s marginal ridges as the direct reference point for measurement. Furthermore, there is a need in the art for a device which directly measures bracket-to-marginal ridges directly that is conveniently hand-held and easy to use.
In order to meet the needs in the art, the present marginal ridge measurement plate has been devised as an attachment to my previous height gauge as described in my aforementioned U.S. Pat. No. 6,296,482. This attachment slides onto the center tab of the height gauge. In use, vertically-extending legs of the marginal ridge measurement plate rest on mesial and distal marginal ridges of the tooth. The plate is shaped so that while the legs rest directly on the marginal ridges, a cut-out portion between the legs avoids contact and interference from the inward-facing slopes of the tooth cusps. The attachment plate is slidably fitted to the head of the height gauge by a slot which is fitted to the center tab or member so that after the bracket is placed on the tooth, the gauge can be moved directly out from the archwire slot without disturbing the bracket position. The slot is centered on a line between the legs and, since the vertically-extending legs of the marginal ridge attachment plate each rests on the mesial and distal marginal ridges, the attachment plate also centers the bracket in the middle of the facial surface of the tooth. Furthermore, the gauge also holds the bracket placement post parallel to the marginal ridges. Thus, the measurement plate not only establishes the correct bracket height but also centers and properly aligns the horizontal angulation of the bracket on the tooth.
More specifically, the applicant has invented a planar measurement plate for attachment to an orthodontic height gauge having a cusp contact tab and a bracket locating post comprising a body portion that includes a rectangular slot adapted to closely and slidably receive the cusp tab. A first pair of vertically-extending legs of substantial length on the attachment include a cut-out region between the legs to avoid contact from inward-sloping sides of the cusp of the tooth when distal ends of the legs are placed against the mesial and distal ridges of the tooth. The attachment may further include a second pair of vertically-extending legs on a second side of the plate opposite the first pair of legs. Furthermore, the attachment may include a total of four pairs of outwardly extending legs each separated 90 degrees and extending from each of four sides of the attachment plate. With each pair of legs separated a different distance apart, that the same attachment may be used to measure the distances of four different sizes of teeth by locating the attachment plate on the height gauge center tab in any one of four different slidable positions. The capability of the attachment plate to achieve four different positions is facilitated by a pair of centrally located slots oriented at 90 degrees from each other. It should be understood that several attachment plates may be provided all having multiple pairs of legs separated by different distances.
Other objects and advantages of the invention will be readily apparent to those of skill in the art from the following drawings and description of the preferred embodiment. For example, the present invention can be used with an implement with non-rotatable heads for placing brackets on models in the laboratory for indirect bonding.